The present invention relates to an electrical lighting fixture. More particularly, the invention is directed to a recessed, ceiling-mounted lighting fixture constituting a sealed enclosure and specially adapted for use in a "clean room" or in a containment environment.
Typically, the present invention is uniquely suited for use where it is required or desired to establish and to maintain an ambient system which is free of materials or substances which are "foreign" to the system sought to be established and maintained. In order to establish and to maintain and perpetuate the pristine and "sterile" atmosphere and environment referred to, it is necessary not only that the electrical fixtures themselves be inert, impervious and completely sealed, but also that the fixtures are so designed, engineered and constructed as to establish, when properly installed, a particulate and fluid-impervious seal with the ceiling itself in which the fixtures are mounted for use.
It will be appreciated that electrical fixtures of the general type referred to are specially desired and sought in broad and diverse places, and for many and exceedingly varied purposes. Typically, lighting fixtures of the type herein described are especially useful in hospitals, in research and development laboratories including biological research laboratories, in laboratories carrying out research and developmental work on sophisticated electrical and/or electronic devices such as computer hardware components, in laboratories, power stations and other establishments where radio-active substances are used, in pharmaceutical plants, as well as in other locales, and to achieve other purposes.
A particularly vexing and challenging problem in the installation of recessed electrical fixtures, for the purposes and uses exemplified above, involves and is posed by "seals" which must be established. Specifically, an end to be achieved is to provide a configuration, design, structure and method of installation which will establish a positive, uninterrupted and sustained and effective seal between the fixture and the outer surface of the ceiling (or other surface) engaged by the fixture when it is inserted in place to assume its recessed disposition.
Some installations, in prior art systems, rely on the use of caulking materials or mastics as interface materials interposed between the fixture and the ceiling to establish seals. The efficacy of such installations is often short lived, due, for example, to drying and shrinking, or general breakdown of the medium employed. Moreover, the sealant composition may itself contribute contaminants to the contained environment. In other arrangements, gaskets have been used. Torsion forces, and bending or bowing of the bounding, gasket-engaging peripheral rim of the fixtures, generated during the process of fixture installation often damage, compromise, and often negate the establishment of a truly effective or sustained seal. Still other installations are unduly complex, while without compensating improvements in operation, and without enhancing efficacy.
It is, therefore, a principal aim of the present invention to obviate shortcomings in prior art recessed electrical fixtures and to provide significant improvements, in not only configuration, construction, and physical composition, but also in the manner and mode by which a more effective and more reliable seal, of increased life, is structured and installed.